1. Field of the Invention
The present invention relates to the filtering of fluids containing solid contaminants and, more particularly, to a high volume self-cleaning industrial pressure filter having a rotatable wiping member for cleansing the filter element of the filter.
2. Description of the Prior Art
Generally, filters have a wide variety of applications from waste water treatment to all types of industrial applications, such as petrochemical, food processing, and materials processing. Filters may be used whenever solid contaminants suspended in the unfiltered liquid may cause malfunction, damage, or must be removed for any other reason. In filters of this type, the fundamental problem is that when no suitable countermeasures are taken, the throughput of filtered liquid through the filter element is drastically reduced in that the filter element openings or apertures are continuously clogged on the inlet side of the filters by the solid contaminants contained in the unfiltered fluid. This problem is aggravated in pressure filters because the solid contaminants tend to be forced into and onto the filtering surface of the filter element and tend to cake over the filtering surface. To clean the filter element, the filter assembly generally requires extensive dismantling which results in a breakdown of operation and high maintenance costs.
Many methods and apparatuses have been used to attempt to self-clean the filter element in order to remove accumulated solid contaminants without the undesirable necessity of intermittent operational shutdowns of the filtering operation. For example, it is well know in the art to remove accumulated solids or sedimentation collected on the filter element during the filtering process by backwashing, in which a portion of the filtered liquid is caused to flow in a reverse direction through the filter element to clean the filter. More recently it has been recognized that the backwashing liquid may be supplied from an external source and at a pressure above the pressure of the fluid in the strainer. Exemplary of this is U.S. Pat. No. 3,074,560.
U.S. Pat. No. 3,357,566 shows a backwash filter having an inlet, a first outlet and a backwash outlet with a backwash arm having rubber edges defining a slot that engages the inside of the filter basket. The filter element is made of a plurality of vertically spaced rods. Similarly, U.S. Pat. No. 4,818,402 shows a backwashing filter having a fixed filter screen and a rotating backwashing apparatus for delivering high velocity liquid for backwashing the filter screen media.
It has also been known to provide a scraping shoe, which advances over the surface of a straining member and removes surface deposits of accumulated solid contaminants which are accumulated and immediately backwashed through a discharge. An example of such filters is shown in U.S. Pat. No. 2,275,958. Similarly, U.S. Pat. Nos. 5,198,111 and 5,569,383 disclose a cleaning unit that simultaneously moves both axially and rotatively along the interior of the filter element and carries a cleaning blade that moves in a conical helical path along the interior face of the filter element for removing accumulated solids.
While all of the above designs have useful applications, their designs are generally complex and typically have multiple seals that are prone to leakage and/or short seal life (which is especially aggravated when the unfiltered liquid is pressurized). Further, the filters heretofore designed and employed have been difficult to service due to the complexity of the design and the time required to separate the filter element from the cleaning components and to remove the cleaning components and the filter element from the housing of the filter.